The use of torsional vibration dampers in power transmitting elements, such as vehicle clutches, is widespread throughout the automotive industry. A conventional construction involves a plurality of circumferentially spaced compression springs acting between the friction disc driving member and the clutch hub driven member. The compression springs both act as the driving connection while providing damping of the transmission gears from vibration and chatter.
In designing a damper for a clutch plate assembly, size limitations control the maximum torque and travel that can be provided. Considerations of damper spring outside diameter, installed length, compressed length, solid length and stress, in combination with the size of the spring windows in the retainer plate, hub and driven plate, to retain and/or provide the required spring compression are necessary. In dampers of the type generally in use today, spacer or stop pins are normally used to attach a drive plate to a retainer plate. The length of the required spring windows determine the amount of space remaining in which to add slots around the spacer pins, which in turn determines the available amplitude for the damper. Current dampers, with equal travel in drive and coast directions, normally have springs which are circumferentially equally spaced.
U.S. Pat. No. 3,091,949 discloses a clutch plate having a design which may provide an amplitude that is approximately double that of a current type damper. However, if no spring change is made in this patent, the resultant damper capacity will be reduced by 50% since two pairs of springs will be operating in series. Since the spring load must be doubled to maintain damper capacity, and assuming that the springs are working at the maximum load, solid length and stress, it becomes necessary to make spring changes, such as increasing outside diameter, installed length, solid length, etc., to provide the requisite spring load with a safe stress. An increase in installed spring length, therefore, results in a reduction in circumferential space required for a slot to accept the stop pins, which has previously been a problem when attempting to increase damper amplitude.